1. Field of the Invention
The present invention relates to an improvement of a motorized roller driven by a driving motor and accompanied with a motor driving circuit, a controller for the motorized roller, a method for controlling the driving motor, a conveyor driven by the motor, and a method for controlling the conveyor.
2. Description of Related Art
It is often the case that a motorized roller incorporating a driving motor is used in a device such as a conveyor. In the motorized roller, a lock of rotation of the incorporated driving motor overloads the driving motor to generate heat in a motor driving circuit or a motor coil, resulting in a possibility of heat damage of the motor driving circuit or the motor coil.
Therefore, a controller for controlling conveyance has been conventionally disposed to protect the motor driving circuit or the motor coil that generates heat in the driving motor, so as to avoid heat damage of the motor driving circuit or the motor coil by halting conveyance by a conveyor or stopping power supply to the motor driving circuit after a certain period of time of a lock of rotation of the driving motor. For example, each of the patent documents 1 and 2 discloses a configuration for limiting current value so as to prevent burnout of the driving motor in the case that the driving motor is trapped or overloaded.
However, a lock of rotation of the driving motor in the motorized roller may be resulted from temporary jam of an article to be conveyed, and thus may be released by clearance of the jam. Therefore, in the case that the jam of an article has caused a lock, it is preferable to continue electric power supply for a few seconds rather than immediately stopping the supply.
As described above, if the driving motor in the motorized roller has become locked, the driving motor is overloaded and the motor driving circuit (especially a power transistor) generates heat. Therefore, conventionally, electric power supply has been stopped or a radiator plate has been in advance disposed in the motor driving circuit so as to avoid heat damage of the driving motor.
However, along with a recent miniaturization trend of components themselves, miniaturized components have been supplied to a motor driving circuit. If a radiator plate is also miniaturized, the heat is not sufficiently radiated, resulting in difficulty in total miniaturization of the motor driving circuit.
Patent Document 1: JP 9-117055A
Patent Document 2: Japanese Patent Publication No. 2538977